3 files changed, 69 insertions, 3 deletions

diff --git a/libjava/java/lang/ClassLoader.h b/libjava/java/lang/ClassLoader.h
index ed6f544..5112eab 100644
--- a/libjava/java/lang/ClassLoader.h
+++ b/libjava/java/lang/ClassLoader.h
@@ -86,6 +86,7 @@ private:
   void checkInitialized();
 public: // actually package-private
   ::java::util::HashMap * __attribute__((aligned(__alignof__( ::java::lang::Object)))) loadedClasses;
+  ::java::util::HashMap * loadingConstraints;
   ::java::util::HashMap * definedPackages;
 private:
   ::java::lang::ClassLoader * parent;
diff --git a/libjava/java/lang/ClassLoader.java b/libjava/java/lang/ClassLoader.java
index 4682dbb..e0463ac 100644
--- a/libjava/java/lang/ClassLoader.java
+++ b/libjava/java/lang/ClassLoader.java
@@ -1,5 +1,5 @@
 /* ClassLoader.java -- responsible for loading classes into the VM
-   Copyright (C) 1998, 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
+   Copyright (C) 1998, 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
 
 This file is part of GNU Classpath.
 
@@ -45,6 +45,7 @@ import gnu.java.util.EmptyEnumeration;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.lang.ref.WeakReference;
 import java.net.URL;
 import java.nio.ByteBuffer;
 import java.security.CodeSource;
@@ -130,6 +131,15 @@ public abstract class ClassLoader
   final HashMap loadedClasses = new HashMap();
 
   /**
+   * Loading constraints registered with this classloader.  This maps
+   * a class name to a weak reference to a class.  When the reference
+   * is non-null, it means that a reference to the name must resolve
+   * to the indicated class.
+   */
+  final HashMap<String, WeakReference<Class>> loadingConstraints
+    = new HashMap<String, WeakReference<Class>>();
+
+  /**
    * All packages defined by this classloader. It is not private in order to
    * allow native code (and trusted subclasses) access to this field.
    */
diff --git a/libjava/java/lang/natClassLoader.cc b/libjava/java/lang/natClassLoader.cc
index 9a687ff..fac1e4d 100644
--- a/libjava/java/lang/natClassLoader.cc
+++ b/libjava/java/lang/natClassLoader.cc
@@ -1,6 +1,6 @@
 // natClassLoader.cc - Implementation of java.lang.ClassLoader native methods.
 
-/* Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006  Free Software Foundation
+/* Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2008  Free Software Foundation
 
    This file is part of libgcj.
 
@@ -41,6 +41,7 @@ details.  */
 #include <java/lang/StringBuffer.h>
 #include <java/io/Serializable.h>
 #include <java/lang/Cloneable.h>
+#include <java/lang/ref/WeakReference.h>
 #include <java/util/HashMap.h>
 #include <gnu/gcj/runtime/BootClassLoader.h>
 #include <gnu/gcj/runtime/SystemClassLoader.h>
@@ -143,7 +144,21 @@ _Jv_RegisterInitiatingLoader (jclass klass, java::lang::ClassLoader *loader)
       // them later.
       return;
     }
-  loader->loadedClasses->put(klass->name->toString(), klass);
+
+  JvSynchronize sync (loader->loadingConstraints);
+
+  using namespace java::lang::ref;
+
+  jstring name = klass->getName();
+  WeakReference *ref = (WeakReference *) loader->loadingConstraints->get (name);
+  if (ref)
+    {
+      jclass constraint = (jclass) ref->get();
+      if (constraint && constraint != klass)
+	throw new java::lang::LinkageError(JvNewStringLatin1("loading constraint violated"));
+    }
+  loader->loadingConstraints->put(name, new WeakReference(klass));
+  loader->loadedClasses->put(name, klass);
 }
 
 // If we found an error while defining an interpreted class, we must
@@ -156,6 +171,46 @@ _Jv_UnregisterInitiatingLoader (jclass klass, java::lang::ClassLoader *loader)
   loader->loadedClasses->remove(klass->name->toString());
 }
 
+// Check a loading constraint.  In particular check that, if there is
+// a constraint for the name of KLASS in LOADER, that it maps to
+// KLASS.  If there is no such constraint, make a new one.  If the
+// constraint is violated, throw an exception.  Do nothing for
+// primitive types.
+void
+_Jv_CheckOrCreateLoadingConstraint (jclass klass,
+				    java::lang::ClassLoader *loader)
+{
+  // Strip arrays.
+  while (klass->isArray())
+    klass = klass->getComponentType();
+  // Ignore primitive types.
+  if (klass->isPrimitive())
+    return;
+
+  if (! loader)
+    loader = java::lang::VMClassLoader::bootLoader;
+  jstring name = klass->getName();
+
+  JvSynchronize sync (loader->loadingConstraints);
+
+  using namespace java::lang::ref;
+
+  WeakReference *ref = (WeakReference *) loader->loadingConstraints->get (name);
+  if (ref)
+    {
+      jclass constraint = (jclass) ref->get();
+      if (constraint)
+	{
+	  if (klass != constraint)
+	    throw new java::lang::LinkageError(JvNewStringLatin1("loading constraint violated"));
+	  // Otherwise, all is ok.
+	  return;
+	}
+    }
+  // No constraint (or old constraint GC'd).  Make a new one.
+  loader->loadingConstraints->put(name, new WeakReference(klass));
+}
+
 
 // Class registration.
 //